Preeclampsia (PE) is a pregnancy-specific systemic multi-organ syndrome. Immune tolerance is very important for the establishment and maintenance of normal pregnancy. More and more studies have proved that the disorder of the complement system is related to the occurrence and development of PE. Complement molecules may be potential markers for PE screening and diagnosis. This review briefly summarized the role and research progress of the complement system in PE, to provide references for the complement molecules as clinical diagnostic markers and prevention target of PE.

Objective:To search for circulating complement-related proteins that predict hypertensive disorders of pregnancy (HDP) based on reports of the development of gestational hypertension and proteinuria and to investigate the role of the complement system in the development of HDP.Methods:A nested case-control study was used, the serum samples of pregnant women who had been given birth or cesarean section in Guangzhou Women and Children′s Medical Center from November 2014 to March 2017 were collected. A total of 60 HDP and 60 normal pregnant women were included and matched 1∶1 by age and gestational week. Unlabeled mass spectrometry was used to screen the differential expression of complement factors in serum samples of 12 pairs of HDP patients and normal pregnancy collected before 20 weeks of pregnancy, and another 48 pairs of serum samples of HDP patients and normal pregnant women were used for preliminary verification. It was selected when the fold change (FC) of complement factor expression was>1.2 or <0.8 and P<0.05. ROC curve was used to evaluate the diagnostic value of corresponding factors. Results:FC of serum C1s, C8 beta chain (C8β) and C1 inhibitor (C1-INH) of HDP patients were 1.19, 1.23, 0.73 ( t=2.07, 2.06, -3.40; P<0.05), respectively. FC of serum C1s, C8 β, C1-INH, factor H-related protein 5 (CFHR5), clusterin (CLU), and C-reactive protein (CRP) of PE patients were 1.39, 1.50, 0.72, 2.49,4.38, and 1.82 respectively ( t=4.36, 5.61, -3.70, 6.82, 8.70, 7.27; P<0.05).The AUC of combining C1s, C8 β and C1-INH was 0.89 in HDP. The AUC of CFHR5, CLU, and CRP in preeclampsia was 0.88, 0.92, and 0.91. Conclusions:Before HDP, the activation and regulation of classic complement pathway and alternative pathway were disordered in pregnant women. The combined detection of complement C1s, C8 β and C1-INH is expected to be used in the prediction of HDP, and CFHR5, CLU, and CRP are expected to be used in the prediction of preeclampsia.